SOLUTION: Thomas drove 60 kilometers at a constant rate of speed. If he had driven 40 kph faster, he would have traveled the same distance for 24 minutes less. How fast did he drive?

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Thomas drove 60 kilometers at a constant rate of speed. If he had driven 40 kph faster, he would have traveled the same distance for 24 minutes less. How fast did he drive?      Log On


   

Question 126901: Thomas drove 60 kilometers at a constant rate of speed. If he had driven 40 kph faster, he would have traveled the same distance for 24 minutes less. How fast did he drive?
Answer by checkley71(8403) About Me  (Show Source):
You can put this solution on YOUR website!
60/x=60/(x+40)+.4
60/x=(60+.4x+16)/(x+40) now cross multiply
60(x+40)=x(60+.4x+16)
60x+2400=60x+.4x^2+16x
.4x^2+16x-2400=0
x^2+40x-6000=0
(x-60)(x+100)=0
x-60=0
x=60 kph. is the speed.
PROOF:
60/60=60/(60+40)+.4
1=(60+40)/100
1=1